Mohamed Mahmoud - Academia.edu (original) (raw)
Papers by Mohamed Mahmoud
In this paper, we propose a novel scheme for efficiently and securely preserving source nodes' lo... more In this paper, we propose a novel scheme for efficiently and securely preserving source nodes' location privacy. Our scheme uses efficient cryptographic operations to change the packets' appearance at each hop to prevent packet correlation. It also creates a cloud with irregular shape of fake traffic to enable the real source node to send its data anonymously to a fake source node to send to the sink and to camouflage the real source node in the nodes creating the cloud. To reduce the energy cost, clouds are active only during data transmission and the intersection of clouds creates a larger merged cloud to reduce the number of fake packets and boost privacy preservation. Simulation and analytical results demonstrate that our scheme can provide stronger privacy preservation than routing-based schemes and requires much less energy cost than global-adversary-based schemes.
International Journal of Computer Trends & Technology, 2019
In the last few years the business intelligence systems (BI) had seen a wide spread among organis... more In the last few years the business intelligence systems (BI) had seen a wide spread among organisations in different sectors such as healthcare and it was studied by many researchers. This study aims to describe what are the business intelligence systems, their benefits and challenges especially when its used in healthcare sector. Moreover, this research suggests that the integration of predictive analytics with BI models could give a better understanding especially regarding the effect of information quality and decision-making quality on the organizational growth and performance.The outcomes of this research show that the main benefits of using BI in healthcare is to improve the decision-making b making it better and faster, enhancing hospitals performance, reducing costs, enhance the quality of healthcare provided to patients, and save time. Moreover, the main challenges in healthcare is the problem of data quality, andthe integration of BI with other hospital systems. Therefore, the analysis of previous BI models shows that there is a consensus that BI system maturity and management quality influence the data and information quality which in turn affect positively the users’ satisfaction, BI usage, and the decision-making quality and lead to improve it. While there is some a contradictory opinion which claim that data quality is no more a challenge and does not affect the success of BI systems. Moreover, BI systems have direct and indirect effect on the decision-making quality but there still no research proving its influence on the organizational growth
Thermosense XXV, 2003
In today"s life, remote environmental sensing via distributed and remote telemetry stations ... more In today"s life, remote environmental sensing via distributed and remote telemetry stations is a vital demand for pollution control and wildlife protection. However the high cost of sensors and their environmental ruggedness, engineering and equipments" cost, and the complex signal processing are restricting the spread of such technology. This paper is introducing the design and modelling of a compact size environmental telemetry station (CETS) based on passive optical sensors and Fuzzy logic control. Here, the cost reduction and size problems are solved by using the fiber Bragg gratings sensors that are able to detect a wide variety of environmental variables such as temperature, humidity, toxic gases, odours, chemical pollution, water dissolved toxins, level, pressure and many more. Also the complex signal processing problem is solved by using an array of fiber Bragg gratings sensors that coexist on a single fiber core, where their signals are multiplexed and processed in the optical domain without the need to analogue-to-digital conversion. The control and encoding problem is solved by using a Fuzzy logic control algorithm within an imbedded system fitted with a CCD sensor spectrometer.
Journal of Materials Science, 2017
Stacking fault energy (SFE) is an intrinsic material property whose value is crucial in determini... more Stacking fault energy (SFE) is an intrinsic material property whose value is crucial in determining different secondary deformation mechanisms in austenitic (face-centered cubic, fcc) steels. Considerable experimental and computational work suggests that the SFE itself is highly dependent-in a complex manner-on chemical composition and temperature. Over the past decades, there have been a large number of efforts focused on determining the composition dependence of SFE in austenitic steel alloys by means of experimental, theoretical or computational methods. Unfortunately, experimental methods suffer from the indirect nature of the methodologies used to estimate the value of SFE, while computational and/or theoretical approaches are either limited by the physics that they can incorporate into the predictions or have more practical limitations associated, for example, to the size of the systems that can be modeled or the assumptions that must be made. In this paper, we review the major experimental and computational approaches to determine SFE in austenitic steel alloys, and we discuss their limitations. We then demonstrate a datadriven machine learning technique to mine the literature of experimental SFE data in steels, while algorithms at the forefront of machine learning have been used to visualize the SFE data and then construct a three-class classifier. The classifier is used then to predict likely secondary deformation mechanisms of untested compositions, while the classifier itself is presented as a valuable tool for the further development of austenitic steel alloys in which the specific secondary plastic deformation mechanisms are a feature to design for. The data as well as the entire analysis workflow are made available to the wider community through a public github repository.
Trabajos de Estadistica, 1991
The three-parameter inverse Gaussian distribution is used as an alternative model for the three p... more The three-parameter inverse Gaussian distribution is used as an alternative model for the three parameter lognormal, gamma and Weibull distributions for reliability problems. In this paper Bayes estimates of the parameters and reliability function of a three parameter inverse Gaussian distribution are obtained. Posterior variance estimates are compared with the variance of their maximum likelihood counterparts. Numerical examples are given.
2009 IFIP International Conference on Wireless and Optical Communications Networks, 2009
Based on an extensive simulation analyses on various optical parameters effect on burst loss rati... more Based on an extensive simulation analyses on various optical parameters effect on burst loss ratio (BLR) for optical burst switching (OBS) networks. A comparison between routing decision based on standard open shortest path first (OSPF) routing protocol and a proposed new OSPF metric is performed. The proposed new OSPF metric takes into account optical parameters in its dependency as number of channels, load and link bandwidth. The result shows better routing decisions leading to better BLR and utilization for OBS networks. Index Terms-Optical burst switching, Routing metric, optical routing, open shortest path first (OSPF), fiber delay line, traffic load, channel bandwidth, number of channels.
Fuel, 2015
ABSTRACT The lowest concentration level of mercury in human body is dangerous for the health due ... more ABSTRACT The lowest concentration level of mercury in human body is dangerous for the health due to its bioaccumulation and high toxicity. Removal of mercury (II) from various samples was explored, studied, optimized and evaluated in the present study by using the combined sorption characteristics of a novel composite based on three sorbent-biosorbent systems. This was accomplished by surface modification of activated carbon with nano-Fe3O4 and loaded with baker’s yeast. The sorbent-biosorbent materials were characterized by using SEM imaging and FT-IR analysis. The magnetic solid phase extraction (MSPE) of Hg(II) from aqueous solutions was studied by measuring the metal sorption capacity and the maximum values were identified in the range of 250-800 μmol g−1. The factors affecting MSPE process of mercury (II) from aqueous solutions were also optimized including the pH, shaking time, interfering ions, sorbent dosage and initial concentration of Hg(II). The potential applications in removal of Hg(II) from different real matrices including water samples and saving lamb waste materials were also explored. The results of this study refer to the excellent percentage extraction values of mercury (II) (92.0-100.0 ± 1.0-3.0%).
Volume 1: 23rd Biennial Conference on Mechanical Vibration and Noise, Parts A and B, 2011
ABSTRACT This paper analyzes a new configuration of a recently proposed “springless” vibration en... more ABSTRACT This paper analyzes a new configuration of a recently proposed “springless” vibration energy harvester. In this study, the harvester is positioned so that its oscillations are aligned vertically acting against gravity. The MPG response is investigated experimentally. Test results show that the VEH behaves as a softening nonlinear oscillator even for small excitations. A mathematical model of the underlying impact oscillator is also derived and its parameters are estimated.
Proceedings of the 39th conference on Design automation - DAC '02, 2002
Reducing power dissipation is one of the most principle subjects in VLSI design today. Scaling ca... more Reducing power dissipation is one of the most principle subjects in VLSI design today. Scaling causes subthreshold leakage currents to become a large component of total power dissipation. This paper presents two techniques for efficient gate clustering in MTC-MOS circuits by modeling the problem via Bin-Packing (BP) and Set-Partitioning (SP) techniques. An automated solution is presented, and both techniques are applied to six benchmarks to verify functionality. Both methodologies offer significant reduction in both dynamic and leakage power over previous techniques during the active and standby modes respectively. Furthermore, the SP technique takes the circuit's routing complexity into consideration which is critical for Deep Sub-Micron (DSM) implementations. Sufficient performance is achieved, while significantly reducing the overall sleep transistors' area. Results obtained indicate that our proposed techniques can achieve on average 90% savings for leakage power and 15% savings for dynamic power.
TheScientificWorldJournal, 2012
Hybrid sorbents and biosorbents were synthesized via chemical and biological treatment of active ... more Hybrid sorbents and biosorbents were synthesized via chemical and biological treatment of active carbon by simple and direct redox reaction followed by surface loading of baker's yeast. Surface functionality and morphology of chemically and biologically modified sorbents and biosorbents were studied by Fourier Transform Infrared analysis and scanning electron microscope imaging. Hybrid carbonaceous sorbents and biosorbents were characterized by excellent efficiency and superiority toward lead(II) sorption compared to blank active carbon providing a maximum sorption capacity of lead(II) ion as 500 μmol g(-1). Sorption processes of lead(II) by these hybrid materials were investigated under the influence of several controlling parameters such as pH, contact time, mass of sorbent and biosorbent, lead(II) concentration, and foreign ions. Lead(II) sorption mechanisms were found to obey the Langmuir and BET isotherm models. The potential applications of chemically and biologically modi...
JAMA otolaryngology-- head & neck surgery, 2013
Positive pressure air is used during basic life support to provide respirations and applied as co... more Positive pressure air is used during basic life support to provide respirations and applied as continuous positive airway pressure to maintain a patent airway during sleep or anesthesia. These functions are more critical in children with obstructive sleep apnea, who often have smaller airway dimensions and increased airway collapsibility. We report 2 cases of boys with Down syndrome and a history of obstructive sleep apnea in whom adverse narrowing of the retroglossal airway is caused by continuous positive airway pressure applied via face mask as documented with magnetic resonance imaging. Administration of continuous positive airway pressure by means of face mask to patients can result in adverse effects on the airway patency by pushing the tongue posteriorly. Awareness of this effect on patients with open mouths and large tongues, as present in Down syndrome, is important for sleep apnea treatment, anesthesia, and emergency respiratory support. Generalization of our observation i...
All Days, 2011
Filter cake characterization is very important in drilling and completion operations. The homogen... more Filter cake characterization is very important in drilling and completion operations. The homogeneity of the filter cake affects the properties of filtration process such as the volume of filtrate, the thickness of filter cake, and the way to remove it. Different models were used to determine the thickness and permeability of the filter cake. These models assume that the filter cake is homogeneous. The objective of this study is to measure the filter cake thickness and permeability of water-based drilling fluids by a new approach and compare the results with previous models. A HPHT filter press was used to perform the filtration process under static conditions (225°F and 300 psi). CT (computed tomography) scan was used to measure the thickness and porosity of the filter cake. SEM was used to provide the morphology of the filter cake. Leica microscope was used to determine particle size distribution. The results obtained from the CT scan showed that the filter cake was heterogeneous ...
SPE Production & Operations, 2011
Summary In-situ-gelled acids that are based on polymers have been used in the field for several y... more Summary In-situ-gelled acids that are based on polymers have been used in the field for several years and were the subject of many laboratory studies. These acids are used in stages to block the treated zone and force the next regular-acid stages to the untreated zones. An extensive literature survey reveals that there are conflicting opinions about using these acids. On one hand, these acids were used in the field, with mixed results. On the other hand, recent laboratory work indicated that these acids can cause damage under certain conditions. The ability of polymer-based in-situ-gelled acids to divert regular acids was studied using a parallel-coreflood setup. The sequence of the injection involved in-situ-gelled acid at 5 wt% hydrochloric acid (HCl) stage followed by regular acid at 15 wt% HCl until acid breakthrough. Experimental results show that flow was initially distributed between the two cores according to the preacid permeability ratio. Permeability grew slightly faster ...
SPE Drilling & Completion, 2012
Summary Filter-cake characterization is very important in drilling and completion operations. The... more Summary Filter-cake characterization is very important in drilling and completion operations. The homogeneity of the filter cake affects the properties of the filtration process such as the volume of filtrate, the thickness of the filter cake, and the best method to remove it. Various models were used to determine the thickness and permeability of the filter cake. Most of these models assumed that the filter cake was homogeneous. The present study shows that the filter cake is not homogeneous, and consists of two layers of different properties. The objective of this study is to measure the filter-cake thickness and permeability of water-based drilling fluids by a new approach and compare the results with previous models. A high-pressure/high-temperature (HP/HT) filter press was used to perform the filtration process under static conditions (225°F and 300 psi). A computed-tomography (CT) scan was used to measure the thickness and porosity of the filter cake. Scanning electron microsc...
Pediatric Emergency Care, 2014
T he authors of the article by Kharazmi et al 1 conclude that propofol sedation of children for a... more T he authors of the article by Kharazmi et al 1 conclude that propofol sedation of children for abdominal computed tomography (CT) scan is relatively safe after a nil per oral period less than the American Society of Anesthesiologists recommended 2 hours. We believe that this conclusion may be premature based on the sample size. The sample of 85 patients sets an upper limit for adverse events of 3.4%. A much larger sample size is needed to justify the conclusion. The authors cite Cravero et al 2 as evidence that the incidence of vomiting and aspiration is very low with use of propofol. Although that may be true, the Cravero article also shows that the overall incidence of airway events is not a low as that of aspiration. Significant desaturation occurred with a 1.54% incidence and laryngospasm occurred at a 0.96% rate. It is also important to note that 99.37% of the sample in the Cravero report had liquid intake more than 2 hours before anesthesia/ sedation and more than 82% had solid intake more than 8 hours prior. It cannot be assumed that a shorter fast will result in the same rate of adverse events. Furthermore, their analysis of the data concludes that the need for timely rescue is significant, implying that unless properly trained individuals are in constant attendance and appropriate monitoring is used, there is the potential for serious adverse events. Before administering sedation for CT scan, the underlying pathology must be
Pediatric Anesthesia, 2008
... Mohamed Mahmoud,; James Spaeth,; Senthilkumar Sadhasivam. Article first published online: 28 ... more ... Mohamed Mahmoud,; James Spaeth,; Senthilkumar Sadhasivam. Article first published online: 28 JUL 2008. ... How to Cite. Mahmoud, M., Spaeth, J. and Sadhasivam, S. (2008), Protection of tongue from injuries during transcranial motor-evoked potential monitoring. ...
New Political Science, 2001
Page 1. New Political Science, Volume 23, Number 1, 2001 Mahmud Muhammad Taha and the Rise and De... more Page 1. New Political Science, Volume 23, Number 1, 2001 Mahmud Muhammad Taha and the Rise and Demise of the Jumhuri Movement* ... Abstract Mahmud Muhammad Taha founded the Jumhuri (Republican) Party in 1945 in the context of the ght for Sudan's independence. ...
Microchimica Acta, 2003
Active silica gel phase (I) was chemically modified to the corresponding amino-(SiNH 2) and chlor... more Active silica gel phase (I) was chemically modified to the corresponding amino-(SiNH 2) and chloro-(SiCl) derivatives via silylation reactions. These were used to synthesize two newly modified silica gel phases (II, III) by direct chemical reaction with 2-hydroxynaphthaldehyde (2-HNA). The surface coverage values are 370, 432 mmol g À 1 and 320, 355 mmol g À 1 for (II) and (III), on the basis of thermal desorption and metal probe testing method, respectively. The metal sorption properties of silica gel phases (II, III) were studied and compared with active silica gel phase (I). The maximum determined metal capacity values were found to be 10-110, 20-290 and 20-370 mmol g À 1 for phases I, II and III, respectively. The distribution coefficient values (K d) were also determined for a series of metal ions, and the results showed that the two new chemically modified phases (II and III) were highly selective for Cu 2 þ , Zn 2 þ , Cd 2 þ , Hg 2 þ and Pb 2 þ. The potential applications of silica gel phases (II, III) as solid phase extractors for the same five metal ions spiked in drinking tap water ($1.000 mg mL À 1) were found to give percentage recovery values in the range of 90.2-96.3 AE 4.1-6.3%, while pre-concentration of the same five metal ions spiked in drinking tap water ($50.0 ng mL À 1) was successfully accomplished with a percentage recovery range of 92.6-95.8 AE 4.8-5.7%.
Journal of Hazardous Materials, 2010
The potential removal and preconcentration of lead (II), copper (II), chromium (III) and iron (II... more The potential removal and preconcentration of lead (II), copper (II), chromium (III) and iron (III) from wastewaters were investigated and explored. Three new alumina adsorbents of acidic, neutral and basic nature (I-III) were synthesized via physical adsorption and surface loading of 1-nitroso-2-naphthol as a possible chelating ion-exchanger. The modified alumina adsorbents are characterized by strong thermal stability as well as resistance to acidic medium leaching processes. High metal up-take was found providing this order: Cu(II)>Cr(III)>Pb(II) owing to the strong contribution of surface loaded 1-nitroso-2-naphthol. The outlined results from the distribution coefficient and separation factor evaluations (low metal ion concentration levels) were found to denote to a different selectivity order: Pb(II)>Cu(II)>Cr(III)) due to the strong contribution of alumina matrix in the metal binding processes. The potential applications of alumina adsorbents for removal and preconcentration of Pb(II), Cu(II), Cr(III) from wastewaters as well as drinking tap water samples were successfully accomplished giving recovery values of (89-100+/-1-3%) and (93-99+/-3-4%), respectively without any noticeable interference of the wastewater or drinking tap water matrices.
Journal of Environmental Science and Health, Part A, 2012
A method is described for hybridization of the adsorption and biosorption characteristics of chem... more A method is described for hybridization of the adsorption and biosorption characteristics of chemically treated commercial activated carbon and baker's yeast, respectively, for the formation of environmental friendly multifunctional sorbents. Activated carbon was loaded with baker's yeast after acid-base treatment. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) Spectroscopy were used to characterize these sorbents. Moreover, the sorption capabilities for lead (II) ions were evaluated. A value of 90 μmol g(-1) was identified as the maximum sorption capacity of activated carbon. Acid-base treatment of activated carbon was found to double the sorption capacity (140-180 μmol g(-1)). Immobilization of baker's yeast on the surface of activated carbon sorbents was found to further improve the sorption capacity efficiency of lead to 360, 510 and 560 μmol g(-1), respectively. Several important factors such as pH, contact time, sorbent dose, lead concentration and interfering ions were examined. Lead sorption process was studied and evaluated by several adsorption isotherms and found to follow the Langmuir and BET models. The potential applications of various chemically and biologically modified sorbents and biosorbents for removal of lead from real water matrices were also investigated via multistage micro-column technique and the results referred to excellent recovery values of lead (95.0-99.0 ± 3.0-5.0 %).
In this paper, we propose a novel scheme for efficiently and securely preserving source nodes' lo... more In this paper, we propose a novel scheme for efficiently and securely preserving source nodes' location privacy. Our scheme uses efficient cryptographic operations to change the packets' appearance at each hop to prevent packet correlation. It also creates a cloud with irregular shape of fake traffic to enable the real source node to send its data anonymously to a fake source node to send to the sink and to camouflage the real source node in the nodes creating the cloud. To reduce the energy cost, clouds are active only during data transmission and the intersection of clouds creates a larger merged cloud to reduce the number of fake packets and boost privacy preservation. Simulation and analytical results demonstrate that our scheme can provide stronger privacy preservation than routing-based schemes and requires much less energy cost than global-adversary-based schemes.
International Journal of Computer Trends & Technology, 2019
In the last few years the business intelligence systems (BI) had seen a wide spread among organis... more In the last few years the business intelligence systems (BI) had seen a wide spread among organisations in different sectors such as healthcare and it was studied by many researchers. This study aims to describe what are the business intelligence systems, their benefits and challenges especially when its used in healthcare sector. Moreover, this research suggests that the integration of predictive analytics with BI models could give a better understanding especially regarding the effect of information quality and decision-making quality on the organizational growth and performance.The outcomes of this research show that the main benefits of using BI in healthcare is to improve the decision-making b making it better and faster, enhancing hospitals performance, reducing costs, enhance the quality of healthcare provided to patients, and save time. Moreover, the main challenges in healthcare is the problem of data quality, andthe integration of BI with other hospital systems. Therefore, the analysis of previous BI models shows that there is a consensus that BI system maturity and management quality influence the data and information quality which in turn affect positively the users’ satisfaction, BI usage, and the decision-making quality and lead to improve it. While there is some a contradictory opinion which claim that data quality is no more a challenge and does not affect the success of BI systems. Moreover, BI systems have direct and indirect effect on the decision-making quality but there still no research proving its influence on the organizational growth
Thermosense XXV, 2003
In today"s life, remote environmental sensing via distributed and remote telemetry stations ... more In today"s life, remote environmental sensing via distributed and remote telemetry stations is a vital demand for pollution control and wildlife protection. However the high cost of sensors and their environmental ruggedness, engineering and equipments" cost, and the complex signal processing are restricting the spread of such technology. This paper is introducing the design and modelling of a compact size environmental telemetry station (CETS) based on passive optical sensors and Fuzzy logic control. Here, the cost reduction and size problems are solved by using the fiber Bragg gratings sensors that are able to detect a wide variety of environmental variables such as temperature, humidity, toxic gases, odours, chemical pollution, water dissolved toxins, level, pressure and many more. Also the complex signal processing problem is solved by using an array of fiber Bragg gratings sensors that coexist on a single fiber core, where their signals are multiplexed and processed in the optical domain without the need to analogue-to-digital conversion. The control and encoding problem is solved by using a Fuzzy logic control algorithm within an imbedded system fitted with a CCD sensor spectrometer.
Journal of Materials Science, 2017
Stacking fault energy (SFE) is an intrinsic material property whose value is crucial in determini... more Stacking fault energy (SFE) is an intrinsic material property whose value is crucial in determining different secondary deformation mechanisms in austenitic (face-centered cubic, fcc) steels. Considerable experimental and computational work suggests that the SFE itself is highly dependent-in a complex manner-on chemical composition and temperature. Over the past decades, there have been a large number of efforts focused on determining the composition dependence of SFE in austenitic steel alloys by means of experimental, theoretical or computational methods. Unfortunately, experimental methods suffer from the indirect nature of the methodologies used to estimate the value of SFE, while computational and/or theoretical approaches are either limited by the physics that they can incorporate into the predictions or have more practical limitations associated, for example, to the size of the systems that can be modeled or the assumptions that must be made. In this paper, we review the major experimental and computational approaches to determine SFE in austenitic steel alloys, and we discuss their limitations. We then demonstrate a datadriven machine learning technique to mine the literature of experimental SFE data in steels, while algorithms at the forefront of machine learning have been used to visualize the SFE data and then construct a three-class classifier. The classifier is used then to predict likely secondary deformation mechanisms of untested compositions, while the classifier itself is presented as a valuable tool for the further development of austenitic steel alloys in which the specific secondary plastic deformation mechanisms are a feature to design for. The data as well as the entire analysis workflow are made available to the wider community through a public github repository.
Trabajos de Estadistica, 1991
The three-parameter inverse Gaussian distribution is used as an alternative model for the three p... more The three-parameter inverse Gaussian distribution is used as an alternative model for the three parameter lognormal, gamma and Weibull distributions for reliability problems. In this paper Bayes estimates of the parameters and reliability function of a three parameter inverse Gaussian distribution are obtained. Posterior variance estimates are compared with the variance of their maximum likelihood counterparts. Numerical examples are given.
2009 IFIP International Conference on Wireless and Optical Communications Networks, 2009
Based on an extensive simulation analyses on various optical parameters effect on burst loss rati... more Based on an extensive simulation analyses on various optical parameters effect on burst loss ratio (BLR) for optical burst switching (OBS) networks. A comparison between routing decision based on standard open shortest path first (OSPF) routing protocol and a proposed new OSPF metric is performed. The proposed new OSPF metric takes into account optical parameters in its dependency as number of channels, load and link bandwidth. The result shows better routing decisions leading to better BLR and utilization for OBS networks. Index Terms-Optical burst switching, Routing metric, optical routing, open shortest path first (OSPF), fiber delay line, traffic load, channel bandwidth, number of channels.
Fuel, 2015
ABSTRACT The lowest concentration level of mercury in human body is dangerous for the health due ... more ABSTRACT The lowest concentration level of mercury in human body is dangerous for the health due to its bioaccumulation and high toxicity. Removal of mercury (II) from various samples was explored, studied, optimized and evaluated in the present study by using the combined sorption characteristics of a novel composite based on three sorbent-biosorbent systems. This was accomplished by surface modification of activated carbon with nano-Fe3O4 and loaded with baker’s yeast. The sorbent-biosorbent materials were characterized by using SEM imaging and FT-IR analysis. The magnetic solid phase extraction (MSPE) of Hg(II) from aqueous solutions was studied by measuring the metal sorption capacity and the maximum values were identified in the range of 250-800 μmol g−1. The factors affecting MSPE process of mercury (II) from aqueous solutions were also optimized including the pH, shaking time, interfering ions, sorbent dosage and initial concentration of Hg(II). The potential applications in removal of Hg(II) from different real matrices including water samples and saving lamb waste materials were also explored. The results of this study refer to the excellent percentage extraction values of mercury (II) (92.0-100.0 ± 1.0-3.0%).
Volume 1: 23rd Biennial Conference on Mechanical Vibration and Noise, Parts A and B, 2011
ABSTRACT This paper analyzes a new configuration of a recently proposed “springless” vibration en... more ABSTRACT This paper analyzes a new configuration of a recently proposed “springless” vibration energy harvester. In this study, the harvester is positioned so that its oscillations are aligned vertically acting against gravity. The MPG response is investigated experimentally. Test results show that the VEH behaves as a softening nonlinear oscillator even for small excitations. A mathematical model of the underlying impact oscillator is also derived and its parameters are estimated.
Proceedings of the 39th conference on Design automation - DAC '02, 2002
Reducing power dissipation is one of the most principle subjects in VLSI design today. Scaling ca... more Reducing power dissipation is one of the most principle subjects in VLSI design today. Scaling causes subthreshold leakage currents to become a large component of total power dissipation. This paper presents two techniques for efficient gate clustering in MTC-MOS circuits by modeling the problem via Bin-Packing (BP) and Set-Partitioning (SP) techniques. An automated solution is presented, and both techniques are applied to six benchmarks to verify functionality. Both methodologies offer significant reduction in both dynamic and leakage power over previous techniques during the active and standby modes respectively. Furthermore, the SP technique takes the circuit's routing complexity into consideration which is critical for Deep Sub-Micron (DSM) implementations. Sufficient performance is achieved, while significantly reducing the overall sleep transistors' area. Results obtained indicate that our proposed techniques can achieve on average 90% savings for leakage power and 15% savings for dynamic power.
TheScientificWorldJournal, 2012
Hybrid sorbents and biosorbents were synthesized via chemical and biological treatment of active ... more Hybrid sorbents and biosorbents were synthesized via chemical and biological treatment of active carbon by simple and direct redox reaction followed by surface loading of baker's yeast. Surface functionality and morphology of chemically and biologically modified sorbents and biosorbents were studied by Fourier Transform Infrared analysis and scanning electron microscope imaging. Hybrid carbonaceous sorbents and biosorbents were characterized by excellent efficiency and superiority toward lead(II) sorption compared to blank active carbon providing a maximum sorption capacity of lead(II) ion as 500 μmol g(-1). Sorption processes of lead(II) by these hybrid materials were investigated under the influence of several controlling parameters such as pH, contact time, mass of sorbent and biosorbent, lead(II) concentration, and foreign ions. Lead(II) sorption mechanisms were found to obey the Langmuir and BET isotherm models. The potential applications of chemically and biologically modi...
JAMA otolaryngology-- head & neck surgery, 2013
Positive pressure air is used during basic life support to provide respirations and applied as co... more Positive pressure air is used during basic life support to provide respirations and applied as continuous positive airway pressure to maintain a patent airway during sleep or anesthesia. These functions are more critical in children with obstructive sleep apnea, who often have smaller airway dimensions and increased airway collapsibility. We report 2 cases of boys with Down syndrome and a history of obstructive sleep apnea in whom adverse narrowing of the retroglossal airway is caused by continuous positive airway pressure applied via face mask as documented with magnetic resonance imaging. Administration of continuous positive airway pressure by means of face mask to patients can result in adverse effects on the airway patency by pushing the tongue posteriorly. Awareness of this effect on patients with open mouths and large tongues, as present in Down syndrome, is important for sleep apnea treatment, anesthesia, and emergency respiratory support. Generalization of our observation i...
All Days, 2011
Filter cake characterization is very important in drilling and completion operations. The homogen... more Filter cake characterization is very important in drilling and completion operations. The homogeneity of the filter cake affects the properties of filtration process such as the volume of filtrate, the thickness of filter cake, and the way to remove it. Different models were used to determine the thickness and permeability of the filter cake. These models assume that the filter cake is homogeneous. The objective of this study is to measure the filter cake thickness and permeability of water-based drilling fluids by a new approach and compare the results with previous models. A HPHT filter press was used to perform the filtration process under static conditions (225°F and 300 psi). CT (computed tomography) scan was used to measure the thickness and porosity of the filter cake. SEM was used to provide the morphology of the filter cake. Leica microscope was used to determine particle size distribution. The results obtained from the CT scan showed that the filter cake was heterogeneous ...
SPE Production & Operations, 2011
Summary In-situ-gelled acids that are based on polymers have been used in the field for several y... more Summary In-situ-gelled acids that are based on polymers have been used in the field for several years and were the subject of many laboratory studies. These acids are used in stages to block the treated zone and force the next regular-acid stages to the untreated zones. An extensive literature survey reveals that there are conflicting opinions about using these acids. On one hand, these acids were used in the field, with mixed results. On the other hand, recent laboratory work indicated that these acids can cause damage under certain conditions. The ability of polymer-based in-situ-gelled acids to divert regular acids was studied using a parallel-coreflood setup. The sequence of the injection involved in-situ-gelled acid at 5 wt% hydrochloric acid (HCl) stage followed by regular acid at 15 wt% HCl until acid breakthrough. Experimental results show that flow was initially distributed between the two cores according to the preacid permeability ratio. Permeability grew slightly faster ...
SPE Drilling & Completion, 2012
Summary Filter-cake characterization is very important in drilling and completion operations. The... more Summary Filter-cake characterization is very important in drilling and completion operations. The homogeneity of the filter cake affects the properties of the filtration process such as the volume of filtrate, the thickness of the filter cake, and the best method to remove it. Various models were used to determine the thickness and permeability of the filter cake. Most of these models assumed that the filter cake was homogeneous. The present study shows that the filter cake is not homogeneous, and consists of two layers of different properties. The objective of this study is to measure the filter-cake thickness and permeability of water-based drilling fluids by a new approach and compare the results with previous models. A high-pressure/high-temperature (HP/HT) filter press was used to perform the filtration process under static conditions (225°F and 300 psi). A computed-tomography (CT) scan was used to measure the thickness and porosity of the filter cake. Scanning electron microsc...
Pediatric Emergency Care, 2014
T he authors of the article by Kharazmi et al 1 conclude that propofol sedation of children for a... more T he authors of the article by Kharazmi et al 1 conclude that propofol sedation of children for abdominal computed tomography (CT) scan is relatively safe after a nil per oral period less than the American Society of Anesthesiologists recommended 2 hours. We believe that this conclusion may be premature based on the sample size. The sample of 85 patients sets an upper limit for adverse events of 3.4%. A much larger sample size is needed to justify the conclusion. The authors cite Cravero et al 2 as evidence that the incidence of vomiting and aspiration is very low with use of propofol. Although that may be true, the Cravero article also shows that the overall incidence of airway events is not a low as that of aspiration. Significant desaturation occurred with a 1.54% incidence and laryngospasm occurred at a 0.96% rate. It is also important to note that 99.37% of the sample in the Cravero report had liquid intake more than 2 hours before anesthesia/ sedation and more than 82% had solid intake more than 8 hours prior. It cannot be assumed that a shorter fast will result in the same rate of adverse events. Furthermore, their analysis of the data concludes that the need for timely rescue is significant, implying that unless properly trained individuals are in constant attendance and appropriate monitoring is used, there is the potential for serious adverse events. Before administering sedation for CT scan, the underlying pathology must be
Pediatric Anesthesia, 2008
... Mohamed Mahmoud,; James Spaeth,; Senthilkumar Sadhasivam. Article first published online: 28 ... more ... Mohamed Mahmoud,; James Spaeth,; Senthilkumar Sadhasivam. Article first published online: 28 JUL 2008. ... How to Cite. Mahmoud, M., Spaeth, J. and Sadhasivam, S. (2008), Protection of tongue from injuries during transcranial motor-evoked potential monitoring. ...
New Political Science, 2001
Page 1. New Political Science, Volume 23, Number 1, 2001 Mahmud Muhammad Taha and the Rise and De... more Page 1. New Political Science, Volume 23, Number 1, 2001 Mahmud Muhammad Taha and the Rise and Demise of the Jumhuri Movement* ... Abstract Mahmud Muhammad Taha founded the Jumhuri (Republican) Party in 1945 in the context of the ght for Sudan's independence. ...
Microchimica Acta, 2003
Active silica gel phase (I) was chemically modified to the corresponding amino-(SiNH 2) and chlor... more Active silica gel phase (I) was chemically modified to the corresponding amino-(SiNH 2) and chloro-(SiCl) derivatives via silylation reactions. These were used to synthesize two newly modified silica gel phases (II, III) by direct chemical reaction with 2-hydroxynaphthaldehyde (2-HNA). The surface coverage values are 370, 432 mmol g À 1 and 320, 355 mmol g À 1 for (II) and (III), on the basis of thermal desorption and metal probe testing method, respectively. The metal sorption properties of silica gel phases (II, III) were studied and compared with active silica gel phase (I). The maximum determined metal capacity values were found to be 10-110, 20-290 and 20-370 mmol g À 1 for phases I, II and III, respectively. The distribution coefficient values (K d) were also determined for a series of metal ions, and the results showed that the two new chemically modified phases (II and III) were highly selective for Cu 2 þ , Zn 2 þ , Cd 2 þ , Hg 2 þ and Pb 2 þ. The potential applications of silica gel phases (II, III) as solid phase extractors for the same five metal ions spiked in drinking tap water ($1.000 mg mL À 1) were found to give percentage recovery values in the range of 90.2-96.3 AE 4.1-6.3%, while pre-concentration of the same five metal ions spiked in drinking tap water ($50.0 ng mL À 1) was successfully accomplished with a percentage recovery range of 92.6-95.8 AE 4.8-5.7%.
Journal of Hazardous Materials, 2010
The potential removal and preconcentration of lead (II), copper (II), chromium (III) and iron (II... more The potential removal and preconcentration of lead (II), copper (II), chromium (III) and iron (III) from wastewaters were investigated and explored. Three new alumina adsorbents of acidic, neutral and basic nature (I-III) were synthesized via physical adsorption and surface loading of 1-nitroso-2-naphthol as a possible chelating ion-exchanger. The modified alumina adsorbents are characterized by strong thermal stability as well as resistance to acidic medium leaching processes. High metal up-take was found providing this order: Cu(II)>Cr(III)>Pb(II) owing to the strong contribution of surface loaded 1-nitroso-2-naphthol. The outlined results from the distribution coefficient and separation factor evaluations (low metal ion concentration levels) were found to denote to a different selectivity order: Pb(II)>Cu(II)>Cr(III)) due to the strong contribution of alumina matrix in the metal binding processes. The potential applications of alumina adsorbents for removal and preconcentration of Pb(II), Cu(II), Cr(III) from wastewaters as well as drinking tap water samples were successfully accomplished giving recovery values of (89-100+/-1-3%) and (93-99+/-3-4%), respectively without any noticeable interference of the wastewater or drinking tap water matrices.
Journal of Environmental Science and Health, Part A, 2012
A method is described for hybridization of the adsorption and biosorption characteristics of chem... more A method is described for hybridization of the adsorption and biosorption characteristics of chemically treated commercial activated carbon and baker's yeast, respectively, for the formation of environmental friendly multifunctional sorbents. Activated carbon was loaded with baker's yeast after acid-base treatment. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) Spectroscopy were used to characterize these sorbents. Moreover, the sorption capabilities for lead (II) ions were evaluated. A value of 90 μmol g(-1) was identified as the maximum sorption capacity of activated carbon. Acid-base treatment of activated carbon was found to double the sorption capacity (140-180 μmol g(-1)). Immobilization of baker's yeast on the surface of activated carbon sorbents was found to further improve the sorption capacity efficiency of lead to 360, 510 and 560 μmol g(-1), respectively. Several important factors such as pH, contact time, sorbent dose, lead concentration and interfering ions were examined. Lead sorption process was studied and evaluated by several adsorption isotherms and found to follow the Langmuir and BET models. The potential applications of various chemically and biologically modified sorbents and biosorbents for removal of lead from real water matrices were also investigated via multistage micro-column technique and the results referred to excellent recovery values of lead (95.0-99.0 ± 3.0-5.0 %).